Chemical reagent



252. COMPOSITIONS,

.No Drawing.

Patented Feb. 11, 1930 Examin PATENT OFFICE FRED H. RHODES, OF ITHACA, NEW YORK CHEMICAL REAGENT Application filed July 18,

The invention relates to inhibitors or restrainers useful in chemical and electrochemical processes for preventing or retardlng the evolution of hydrogen at the surfaces of metals immersed in the solution or for otherwise preventing or retarding the chemical action of acids on metals. The invention is particularly applicable to chemical processes wherein metals such as iron, steel, nickel, etc., are subjected to the action of acids for removin scale, rust or oxide from the surfaces thereo Such processes are often referred to as pickling processes and are widely used in manufacturing establishments.

My invention consists in the discovery of a. series of chemical compounds which when added to certain chemical reagents act to inhibit the undesired reactions of said reagents without interfering with the desired reactions thereof. For instance when added to a pickling bath of a composition that would ordinarily have a corrosive action upon metals, such compounds serve to retard the corrosive action on the metals and the consequent evolution of hydrogen without interfering materially with the desired function of dissolving the oxide, rust or scale found on the surface of the metal.

There are many advantages in the use of a pickling bath having incorporated therein an inhibiting agent for retarding the chemical action of the acid on the metal. For example, such a. composition is useful in removing the layer of iron oxide which is formed on steel or iron during the rollin of sheets, the drawing of wires or rods, t e spinning of thin shapes and the annealing of shapes prior to an application of a coating of vitreous enamel, glass, tin, zinc or other metal or paint, varnish enamel, lacquer or other protective or decorative coating. Another use of the process is in the removing of the metallic oxide or carbonate forming on copper or other nonferrous materials. Another advantageous use is in eliminating the scale forming in pipes and in the tubes of automobile radiators which often seriouslyinterferes withthe proper flow and circulation of the fluid through the radiator. My invention is applicable generally to the removal of oxides and scales from 1929. Serial N0. 379,319.

metals by a pickling process and the use of the inhibiting agents not only prevents or diminishes the attack of the metals themselves by the acid but also creates more healthful working conditions surrounding the pickling bath. The evolution of hydrogen gas, which is an incident of the attack of the metal by the acid, results in the carrying into the surrounding air of a certain amountof the acid of the bath in the form of a spray which is injurious to the operators and wasteful of the acid material.

In its broader aspects, my invention contemplates the use of the inhibiting agents hereinafter more fully described in connection with any chemical or electrochemical solution or reagent which under normal conditions of operation will evolve hydrogen at the surface of a metal immersed therein. In other Words, my invention provides a means for causing desired chemical or electrochemical reactions to take place and without substantially decreasing the rate of said reactions causing an inhibiting action retarding or actually preventing the evolution of hydrogen which would normally take place Without the presence of the inhibiting agents.

As a further example of the utility of my invention, it may sometimes be found desirable to use the new inhibiting agents in connection with electroplating processes. It is well known that in the electrodeposition of certain metals hydrogen is liberated at the cathode in addition to the metal which it is desired to plate. By using the inhibiting agents in accordance with my invention the evolution of hydrogen at the cathode may be retarded without correspondingly retarding the deposition of the metal. Thus the efliciency of the plating process is increased and certain undesirable characteristics of the plated metal caused by the evolution of hy drogen may be eliminated.

The new inhibiting agents forming the subject matter of this application may be broadly classified as derivatives of acridine containing attached to the acridine nucleus at least one radical having a nitrogen atom. While there are a number of compounds coming within the purview of this invention, I will van-Wm w...

refer more specifically to some of the more important compounds with which I have made careful tests to determine the degree of inhibiting power possessed thereby.

The following substances are examples of compounds which have been tested and found to have markedly superior inhibiting properties to acridine itself:

3,6-diaminoacridine I 3,6-dimethyl-2,7-diaminoacridine ethylchloride N cmt $1 The compounds mentioned above may ordinarily be used as inhibiting agents either in the pure state or in the relatively impure form resulting from commercial methods of manufacturing the same. It has been found that in many cases the impure compounds are more efficient inhibitors than the chemically pure substances. This may possibly be due to the presence of small amounts of more complex derivatives in the impure material.

The inhibiting compounds may be introduced into the chemical reagent not only in the form of a free base as indicated in some of the formulas given above, but may also be used in the form of a salt as, for example, the hydrochloride of the base.

The amount of the inhibiting agent to be used for any given chemical solution depends not only upon the efliciency of the inhibiting agent but also on operating conditions and the exact results desired in the particular process.

In general it may be said that with the compounds mentioned above as the inhibiting agents, 1% or less of the compound added to the solution will be sufiicient to obtain the maximum efiect although there is apparently no disadvantage other than increased cost in adding larger amounts if so desired. There is, however, a certain relation between the amount of inhibiting agent added and its efficiency.

For example it has been found that when 3,6-diaminoacridine is added to a pickling bath containing 7.5% sulphuric acid there is an inhibiting action of the acid on iron to the extent of 95.4% at 60 C. when 3,6;diaminoacridine is present in the proportion of 10 millimols per liter of solution.

It has also been found that 10 millimols per liter of phosphine GN added to a 7 solution of sulphuric acid will give 99.7% inand two amino groups substituted on the acridine nucleus. This compound probably has the structural formula denoted by the name 3,6-dimethy1-2,7-diaminoacridine ethylchloride'. Also it probably contains some salt and perhaps other impurities.

The amount of inhibiting action desired may vary for different manufacturing conditions. For example, in pickling thin sheet steel for light enameled ware it is desirable to use sufiicient inhibitor to effect as much as 98% inhibition, whereas in pickling thicker sheets for heavy enamel as little as 80% inhibition might be desired. Thus according to my invention, the inhibiting agent may be added in amounts sufficient only to retard the evolution of hydrogen or on the other hand a suitable inhibiting agent of high efficiency may be added in larger amounts in order to substantially prevent the evolution of hydrogen.

From the above description it will be noted that my invention relates to the discovery 01 a series of cyclic organic nitrogen compounds having inhibiting characteristics rendering them very valuable in chemical and electrochemical processes with which they have never heretofore been associated. lVhile I have described certain compounds and certain processes with particularity, it is to be understood that the invention is not necessarily limited thereby except in the light of the claims appended hereto.

What I claim as my invention is:

1. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine containing attached to to the acridine nucleus at least one radical containing a nitrogen atom, said nitrogen atom being attached to the acridine nucleus.

2. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine containing attached to the acridine nucleus at least one radical contaming a trivalent nitrogen atom, said nitrogen atom being attached to the acridine nucleus.

3. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine containing attached to the acridine nucleus at least one amino radical.

4. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent 3.6 dimethyl 2.7 diamino acridine.

5. The process of inhibiting or restraining 252. COMPOSITIONS,

the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducinginto the liquid reagent an addition product of 3.6 dimethyl 2.7 diamino acridine.

6. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a salt-like addition product of 3.6 dimethyl 2.7 diamino acridine.

7. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the diquid reagent 3.6 dimethyl 2.7 diamino acridine ethyl chloride.

8. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent the material known as phosphine GN which is a brown powder consisting of the ethyl chloride of an organic base derived from acridine by substituting two methyl groups and two amino groups in an acridine nucleus.

9. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or re strainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine containing attached to the acridine nucleus at least one radical containing a nitrogen atom, said nitrogen atom being attached to the acridine nucleus.

10. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine containing attached to the acridine nucleus at least one radical containing a trivalent nitrogen atom, said nitrogen atom being attached to the acridine nucleus.

11. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a deriva tive of acridine containing attached to the acridine nucleus at least one amino radical.

12. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising 3.6 dimethyl 2.7 diamino acridine.

13. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising an addition product of 3.6 dimethyl 2.7 diamino acridine.

14. A liquid bath for chemical or electro chemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed thereinandaninhibitoror restrainer in said solution for diminishing the evolution of hydrogen comprising a salt-like addition product of 3.6 dimethyl 2.7 diamino acridine.

15. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising 3.6 dimethyl 2.7.

diamino acridine ethyl chloride.

16. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising the material known as phosphine GN which is a brown powder consisting of the ethyl chloride of an organic base derived from acridine by substituting two methyl groups and two amino groups in an acridine nucleus.

In testimony whereof I afiix my signature.

FRED H. RHODES. 

